The present invention relates to a composite refractory member having therethrough a discharge opening and for use in discharging molten material, particularly molten metal, from a vessel, particularly a metallurgical vessel. The present invention particularly is directed to such a refractory member which may be employed as a movable or stationary plate assembly in a sliding closure unit, or as an inlet or outlet nozzle in such sliding closure unit. More particularly, the present invention is directed to such a refractory member of the type having at least one insert which at least partially defines the discharge opening of the refractory member and which is formed of an oxide ceramic material having a high resistance to the molten material, and a refractory base structure enclosing and supporting the insert.
Furthermore, the present invention is directed to a method for the formation of such a refractory member.
West German DE-AS No. 27 19 105 discloses a refractory plate assembly including an oxide ceramic insert enclosed by a refractory base structure of refractory concrete. The insert is of an oxide ceramic material particularly adapted to withstand the molten metal, and particularly the insert is formed of MgO, Cr.sub.2 O.sub.3, Al.sub.2 O.sub.3 or ZrO.sub.2 or a mixture of such oxides. On the other hand, the refractory concrete of the base structure is composed of 70 to 95 weight percent tabular alumina and 5 to 30 weight percent of alumina cement with a content of 80 to 96 weight percent of Al.sub.2 O.sub.3.
This and similar alumina compositions are employed for the refractory concrete due to the relatively high thermal shock resistance of such materials. However, the use of such refractory concrete compositions has certain inherent disadvantages. Thus, such materials have low corrosion resistance to molten metals, and this is a problem when a molten metal contacts a base structure formed of such composition. This can occur, for example, when the two plates of a sliding closure unit are formed of composite refractory members. Specifically, it can occur that the molten metal will penetrate between the two plates and come into contact with the base structures. Further, such alumina compositions have relatively low friction resistance.
In view of the above disadvantages of conventional alumina compositions, it would be desirable to form the base structure of a refractory concrete having greater abrasion resistance and resistance to erosion by molten metal. However, refractory concretes of such type, for example magnesia, have a relatively low thermal shock resistance and therefore have been considered to be too brittle for use as a refractory concrete for forming a base structure of a composite refractory member of this type.